Detecting relayed communications

ABSTRACT

Methods, apparatus and computer readable code for determining whether a potential relay device is a relay device are provided herein. In some embodiments, first and second information elements are received from a potential relay device, which is an original source of the second information element. In order to determine whether the potential relay device is a relay device, it is determined whether a feature of an original source of the first information element and a feature of the potential relay device are features unlikely to relate to a single device, wherein a positive result of the determining is indicative that the potential relay device is a relay device. In an exemplary embodiment, a disclosed system includes an information element receiver and a feature incompatibility analyzer. Optionally, the disclosed system includes a feature discovery module, a parameter obtainer and a feature database.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/630,494, filed Feb. 24, 2015, which is a continuation of U.S. patentapplication Ser. No. 10/585,517, filed Jul. 10, 2006, now issued as U.S.Pat. No. 8,966,088, which is a National Stage entry of PCT/IL05/00033,filed Jan. 9, 2005, which claims priority to U.S. ProvisionalApplication Ser. No. 60/534,927, filed Jan. 9, 2004, all of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to methods, apparatus and computerreadable code for detecting relayed communications.

BACKGROUND OF THE INVENTION

Relay devices are commonly used in many communication mediums andenvironments, and especially on the Internet. A relay device is acommunication device that receives communications from a sender andforwards them to a receiver.

A relay device may be used in cases where direct communication betweenthe sender and receiver is not possible, or to enhance the performanceand security of various applications.

For example, users in a secure environment (e.g. a private corporatedata network) may be prohibited from connecting directly to HTTP servers(see RFC 2616; for information about the RFC series of documents see theRFC Editor website at http://www.rfc-editor.org) on the public Internet.In such cases an HTTP proxy server may be installed in the securenetwork, and will be allowed to connect to outside HTTP servers. Userscan then use the proxy to relay HTTP requests and responses to and fromexternal HTTP servers. In this example, the HTTP proxy server is a relaydevice. In another example, users on a small network (e.g. a homenetwork) may use a SOCKS proxy (see RFC 1928) to connect to the Internetfrom multiple personal computers using one Internet connection with asingle IP address (see RFC 791). In this example, the SOCKS proxy is arelay device. In another example, some HTTP proxies serve as cacheproxies, by storing local copies of the content they receive and thenserving requests for the same content from local storage. By doing that,cache proxies reduce the number of requests sent to remote servers. Inanother example, HTTP proxies serve as content filtering proxies, bydenying users' access to objectionable materials.

Besides these normal uses, relay devices are often exploited formalicious purposes.

For example, a malicious user (attacker) will use a relay device to hidehis real IP address. IP addresses are often used to expose the identityof an attacker by examining Internet Service Provider (ISP) records toreveal who used the IP address at the time of the attack. Since theattacked party sees the communications as originating from the relaydevice's IP address, the attacker remains anonymous and is less likelyto suffer consequences (e.g. losing his ISP account or gettingarrested). This technique is often used by hackers, fraudsters andscammers.

An attacker may also use several relay devices at once by instructingone relay device to connect to another relay device and so on, andinstructing the last relay device to connect to the target. Thisprotects the attacker in case the operator of the last relay device isasked to provide the IP address used in the attack.

In another example, an attacker will use a large number of relay devicesto create the illusion that communications are originating from manydifferent users. Attackers use this technique to circumvent anti-abusesystems that block IP addresses based on the rate of potentially abusiveactions they make (i.e. number of actions made in a time period). Forexample, many online services that use passwords to authenticate theirusers will block an IP address after a few failed login attempts, inorder to prevent brute force attacks. In a brute force attack, anattacker attempts to recover a password by trying many differentpasswords until a successful login. In another example, many onlineservices which provide access to a directory of personal informationwill block an IP address if the rate of queries it sends exceeds acertain limit, in order to prevent attackers from harvesting largeamounts of personal information, which can be used for other abusiveactions such as sending spam (unsolicited electronic messages). Inanother example, anti-spam systems will block IP addresses that send ahigh volume of messages. In another example, since web sites can getpaid for each time a user views an online advertisement (or click onit), online advertising companies will ignore large numbers ofadvertisement views (or clicks on advertisements) that originate fromthe same IP address, to prevent scammers from generating false views of(or clicks on) advertisements.

By using multiple relay devices, scammers circumvent these defenses.

In another example, an attacker will use a relay device to create theillusion that he is located in a different geographical location. Sincemany online credit card fraud attempts originate from outside the UnitedStates, many US online merchants will not accept foreign credit cards orship products abroad. Fraudsters can overcome these barriers by using UScredit cards and shipping to accomplices in the US. Merchants respondedby rejecting orders in which the geographic location of the IP address(as reported by IP geo-location services such as GeoPoint offered byQuova, Inc. of Mountain View, Calif., USA; See U.S. Pat. Nos. 6,684,250and 6,757,740), does not match the address or addresses provided in theorder (e.g. the credit card billing address is in the US, while the IPaddress is in Indonesia). Fraudsters overcome this barrier by usingrelay devices in acceptable locations.

While properly configured relay devices usually implement access controlmechanisms to allow access only to authorized users, many relay devicesare globally accessible (known as ‘open proxies’) and are abused byattackers. In some cases, open proxies exist because they are shipped aspart of a hardware device or software and were unknowingly installed bytheir owners, or because administrators have mistakenly or carelesslyconfigured relay devices to relay communications from unauthorizedsources. In other cases the open proxy is maliciously installed withoutthe permission of the computer owner, such as by sending a ‘TrojanHorse’ to the computer's owner, by a computer virus, or by manuallyhacking into the computer (hacking is the act of exploiting amalfunction or misconfiguration to gain control over the computer).

Since relay devices, and especially globally accessible relay devicesare often used for malicious purposes, many online service providers andmerchants treat any communication received through a relay device asmalicious. For example, many SMTP servers (see RFC 821) will not acceptemails received through relay devices, many IRC servers (see RFC 2810)will not accept users connected through relay devices, and some Internetmerchants will not accept orders received through relay devices.

Current methods for determining whether a communication is being relayedthrough a relay device are based on examining whether communicationsfrom the source IP address of the communication are typical to a relaydevice (assuming the relay device reports its own source IP address inthe relayed communication).

One such method is examining whether an HTTP communication contains HTTPheaders unique to relay devices. Examples of such headers include‘X-Forwarded-For’,‘X-Originating-IP’, ‘Via’, ‘X-Cache’ and ‘Client-IP’.This method is limited in that it cannot be used when the relayedprotocol is not HTTP. It is further limited in that not all relaydevices report such headers, especially if relaying is performed at alevel below HTTP, as is the case with SOCKS proxies or when using theHTTP CONNECT method (see RFC 2817).

Another method is to attempt to connect back to the source IP address(create a ‘backward connection’) using an agreed upon protocol, which isnot likely to be implemented by relay devices. For example, many IRCservers will attempt to connect back to the source IP address using theIdentification Protocol (see RFC 1413), which most IRC clientsimplement. Since relay devices are not likely to implement theIdentification Protocol, receiving an indication from the source IPaddress that the connection attempt was successful (e.g. a TCP segmentcontaining the SYN and ACK control flags; for an explanation of TCP seeRFC 793) would indicate that the communication is most likely not beingrelayed. This method is limited in that service providers and users mustagree on a protocol that would be used for backward connections, in thatservice providers must originate a connection to every user using theagreed upon protocol, and in that every user must operate a server toaccept such connections.

Another method involves creating a backward connection to the source IPaddress using protocols and port numbers commonly used for relay devices(e.g. SOCKS on TCP port 1080 or HTTP on TCP port 8080) and thenattempting to relay a communication. Since most users do not operateglobally accessible communication relays on their computers, asuccessful attempt would indicate that the user is most likely using arelay device. This method is limited in that service providers mustoriginate backward connections to every user, and in that a multitude ofbackward connections are required to cover a significant portion of therelay devices configurations possible. This method is further limited inthat creating multiple backward connections is a resource consumingoperation, and may be regarded unethical, abusive or otherwiseproblematic.

In an effort to alleviate the limitations of the current methods, onlineservice providers cooperate with each other by sharing information aboutrelay devices. For example, service providers often query databases(known as ‘blacklists’) that list various communication parameters ofglobally accessible communication relays, as discovered by other serviceproviders or by the database operators, for example to check if a givensource IP address is listed. Such a database is the MAPS Open ProxyStopper maintained by Mail Abuse Prevention System LLC of San Jose,Calif., USA. These databases are as limited as the methods used topopulate them, and are further limited by not being always up to date.

There is an apparent need for an effective method to determine whether acommunication is being relayed through a relay device.

BRIEF SUMMARY OF THE INVENTION

It is now disclosed for the first time a method for determining whetherinformation elements received from a potential relay device have beenrelayed through a relay device. The disclosed method of determiningwhether a potential relay device is a relay device includes receivingfirst and second information elements from the potential relay device,wherein the potential relay device is an original source of the secondinformation element.

In some embodiments, the disclosed method further includes determiningwhether a feature of an original source of the first information elementand a feature of the potential relay device are features unlikely torelate to a single device. In some embodiments, the disclosed methodfurther includes determining whether a feature of an original source ofthe first information element and a feature of the potential relaydevice are features unlikely to describe a single device.

Several features of transmitters and original sources of informationelements that are surprisingly useful for determining if a receivedinformation element has been relayed are disclosed herein. Features oftransmitters and original sources of information elements useful fordetecting if a received information element has been relayed include butare not limited to a configuration status of a device, communicationsperformance of a device, a feature of a related DNS request, and alatency parameter such as a round trip time to a transmitter and/ororiginal source of information elements.

According to some embodiments, the second information element is of atype that a relay device of a class of relay devices is unlikely torelay.

According to some embodiments, the first information element is of atype that a relay device of a class of relay devices is likely to relay.

Exemplary classes of relay devices relevant for embodiments of thepresent invention include, but are not limited to, SOCKS proxies, HTTPproxies including HTTP proxies using a GET method and/or a CONNECTmethod, IP routers and Network Address Translation devices.

According to some embodiments, the first information element and/orsecond information element are part of a communication of a typeselected from the group consisting of IP, TCP, ICMP, DNS, HTTP, SMTP,TLS, and SSL. According to some embodiments, the first and secondinformation elements are parts of a single communication.

According to some embodiments, the first and second information elementsare sent in two different layers of a protocol stack.

According to some embodiments, the stage of determining includesdiscovering the feature of an original source of the first informationelement, and discovering the feature of the potential relay device.

According to some embodiments, the stage of determining further includescomparing the feature of the original source of the first informationelement with the feature of the potential relay device.

Thus, in one illustrative example, a configuration status parameter suchas an operating system is determined both for an original source of thefirst information element, and for the potential relay device. If adiscrepancy is discovered between configuration status parameters of theoriginal source of the information packet and the potential relaydevice, this is unlikely to indicate a single device, and it is thusdeduced that the potential relay device is not the same device as theoriginal source device, but rather a separate relay device.

In some embodiments, the method comprises obtaining a parameterindicative of the feature of an original source of the first informationelement, and obtaining a parameter indicative of the feature of thepotential relay device.

Thus, it is noted that it is not necessary to explicitly obtainknowledge of the features of the source of the first information elementand the source of the potential relay device. In a specific example, adifferential latency between the potential relay device and the sourceof the first information element is obtained, without necessarilyobtaining the individual latencies.

In some embodiments, the method includes obtaining a parameterindicative of a relationship between the feature of the original sourceof the first information element and the feature of the potential relaydevice.

In some embodiments, the stage of determining includes analyzing theparameter indicative of a relationship between the feature of theoriginal source of the first information element and the feature of thepotential relay device

In some embodiments, the parameter is obtained from at least one of thefirst information element and the second information element.

According to some embodiments, the method further comprises sending anoutgoing communication to at least one of the original source of thefirst information element and the potential relay device, and receivinga third information element from at least one of the original source ofthe first information element and the potential relay device.

According to some embodiments, the method further includes deriving fromthe third information element information related to a feature of atleast one of the original source of the first information element andthe potential relay device.

According to some embodiments, the method further includes verifyingthat an original source of the third information element is the originalsource of the first information element

According to some embodiments, the method further includes verifyingthat an original source of the third information element is thepotential relay device.

In one exemplary embodiment, after receiving first and secondinformation elements that may have been relayed, an HTTP response and aping are returned to the purported source of the communication.Irrespective of the presence of an intermediate relay device, the HTTPresponse is relayed by the relay device to the original source of thecommunications, which in turn, returns a third information element. Incontrast, the relay device responds to the ping without forwarding theping to the original source of the first information element. Thus, widedifferential in latencies is indicative of the presence of a relaydevice.

According to some embodiments, the method further includes receiving athird information element from the potential relay device, and derivingfrom the third information element information related to a feature ofthe potential relay device.

According to some embodiments, the method further includes receiving athird information element from the source of the first informationelement and deriving from the third information element informationrelated to a feature of a source of the first information element.

According to some embodiments, at least one of the feature of a sourceof the first communication and the feature of the potential relay deviceis a feature related to a configuration status.

Exemplary features related to a configuration status include but are notlimited to an operating system type, an operating system version, asoftware type, an HTTP client type, an HTTP server type, an SMTP clienttype, an SMTP server type, a time setting, a clock setting and a timezone setting.

According to some embodiments, the stage of determining includesexamining a parameter indicative of the feature related to aconfiguration status.

Exemplary parameters indicative of the feature related to aconfiguration status include but are not limited to HTTP ‘User-Agent’header, An RFC 822 ‘X-Mailer’ header, An RFC 822 ‘Received’ header, AnRFC 822 ‘Date’ Header, a Protocol implementation manner, a TCP/IP StackFingerprint, an IP address, a TCP port, a TCP Initial Sequence number, aTCP Initial Window, a Whois record, a Reverse DNS record, and a rate ofacknowledged information.

According to some embodiments, at least one of the feature of a sourceof the first communication and the feature of the potential relay deviceis a feature related to communication performance.

According to some embodiments, the feature related to communicationperformance is selected from the group consisting of a measuredcommunication performance, a measured relative communicationperformance, and an estimated communication performance.

According to some embodiments, the feature related to communicationperformance is selected from the group consisting of a latency of acommunication, a latency of an incoming communication, a latency of anoutgoing communication, a communication rate, an incoming communicationrate, an outgoing communication rate, incoming maximum communicationrate, and an outgoing maximum communication rate.

According to some embodiments, the stage of determining includesexamining a parameter indicative of the feature related to communicationperformance.

According to some embodiments, the parameter is selected from the groupconsisting of time of receipt of an information element, time of sendingof an information element, a round trip time, a roundtrip time gap, anIP address, a Whois record, a Reverse DNS record, and a rate ofacknowledged information.

According to some embodiments, a higher round trip time gap isindicative of a higher likelihood that a relay device is being used formalicious purposes.

According to some embodiments, at least one of the feature of a sourceof the first information element and the feature of the potential relaydevice is selected from the group consisting of a sub-network, a networkadministrator, and a geographic location.

According to some embodiments, the determining includes examining aparameter indicative of at least one of the feature of a source of thefirst communication and the feature of a source of the secondcommunication, and the parameter is selected from the group consistingof an HTTP “User-Agent” header, an RFC 822 ‘X-Mailer’ header, an RFC 822‘Received’ header, an RFC 822 ‘Date’ Header, an IP address, a WHOISrecord, and a reverse DNS record.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesreceiving first and second information elements from the potential relaydevice, wherein the potential relay device is an original source of thesecond information element, and analyzing a configuration status of anoriginal source of at least one of the first and the second informationelements, wherein the configuration status is selected from the groupconsisting of an operating system type, an operating system version, asoftware type, an HTTP client type, an HTTP server type, an SMTP clienttype, an SMTP server type, a time setting, a clock setting, and a timezone setting.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesreceiving first and second information elements from the potential relaydevice, wherein the potential relay device is an original source of thesecond information element, and analyzing a feature related tocommunication performance of an original source of at least one of thefirst and the second information elements.

According to some embodiments, the feature related to communicationperformance is selected from the group consisting of a latency of acommunication, a latency of an incoming communication, a latency of anoutgoing communication, a round trip time of a communication, acommunication rate, an incoming communication rate, an outgoingcommunication rate, incoming maximum communication rate, and an outgoingmaximum communication rate.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisessending a message to the potential relay device inducing a finalrecipient of the message to send an outgoing DNS request, anddetermining from the outgoing DNS request whether the potential relaydevice is a relay device.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesreceiving first and second information elements from the potential relaydevice, wherein the potential relay device is an original source of thesecond information element; and checking whether a round trip time tothe potential relay device is significantly different than a round-triptime to an original source of the first information element.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesreceiving first and second information elements from the potential relaydevice, wherein the potential relay device is an original source of thesecond information element; and checking whether an operating system ofthe potential relay device is different than an operating system of anoriginal source of the first information element.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesreceiving first and second information elements from the potential relaydevice, wherein the potential relay device is an original source of thesecond information element, and checking whether a location of thepotential relay device is different than a location of an originalsource of the first information element.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesreceiving first and second information elements from the potential relaydevice, wherein the potential relay device is an original source of thesecond information element; and checking whether an administrator of thepotential relay device is different than an administrator of an originalsource of the first information element.

It is now disclosed for the first time a method of determining whether apotential relay device is a relay device. The disclosed method comprisesdetermining whether a feature of an original source of a firstinformation element and a feature of the potential relay device arefeatures unlikely to relate to a single device, wherein the potentialrelay device is a transmitter of the first information element and of asecond information element, wherein the potential relay device is anoriginal source of the second information element, and wherein apositive result of the determining is indicative that the potentialrelay device is a relay device.

It is now disclosed for the first time a method of determining whetherreceived information was relayed by a relay device. The disclosed methodcomprises determining from the received information element acommunications performance measurement, and generating from results ofthe determining output indicative of whether the received informationwas relayed by the relay device.

It is now disclosed for the first time a method of determining whetherreceived information was relayed by a relay device. The disclosed methodcomprises determining from the received information element a parameterindicative of communications performance, and generating from results ofthe determining output indicative of whether the received informationwas relayed by the relay device.

Exemplary determined communication performance measurements include butare not limited to a latency of communication with a monitored host, anincoming latency of communication with a monitored host, an outgoinglatency of communication with a monitored host, a communication rate, anincoming communication rate, an outgoing communication rate, incomingmaximum communication rate, and an outgoing maximum communication rate.

It is now disclosed for the first time a system for determining whethera potential relay device is a relay device. According to someembodiments, the disclosed system includes an information elementreceiver, for receiving information elements from a plurality of devicesincluding an information source device and the potential relay device,and a feature incompatibility analyzer, for determining whether afeature of the information source device and a feature of the potentialrelay device are features unlikely to relate to a single device.

According to some embodiments, the system further includes a featurediscovery module, for discovering at least one feature selected from thegroup consisting of a feature of the information source device and afeature of the potential relay device.

Optionally, the information element receiver is further configured toreceive information elements from a monitored host.

Optionally, the system includes an outgoing information element sender.

According to some embodiments, the system further includes a parameterobtainer, for obtaining at least one parameter selected from the groupconsisting of a parameter indicative of a feature of an informationsource device, a parameter indicative of a feature of the potentialrelay device, and a parameter indicative of whether a feature of theinformation source device and a feature of the potential relay deviceare features unlikely to relate to a single device.

According to some embodiments, the system further includes a featuredatabase for storing a map between pairs of features and data indicativeof whether the pairs of features are incompatible features.

These and further embodiments will be apparent from the detaileddescription and examples that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 provides an illustration of an environment in which a RelayDetection System operates according to some embodiments of the presentinvention.

FIG. 2A provides a diagram of a Potential Relay Device sendingInformation Elements to Relay Detection System.

FIG. 2B provides a diagram of the original sources of informationelements received by a Relay Detection System according to someembodiments of the present invention.

FIG. 2C provides a diagram of the case wherein Potential Relay Device isInformation Source Device.

FIG. 2D provides a diagram of the case wherein Potential Relay Deviceand Information Source Device are distinct devices.

FIG. 3 provides a description of a system according to severalembodiments of the present invention.

FIG. 4A describes the latencies of communications between InformationSource Device and Monitored Host in the case where Relay Device is beingused.

FIG. 4B describes the latencies of communications between InformationSource Device and Monitored Host in the case where Relay Device is notbeing used.

FIG. 5A provides a diagram of the case in which Information SourceDevice sends two information elements, Potentially Relayed InformationElement 1 and Potentially Relayed Information Element 2, directly toMonitored Host, without using Relay Device.

FIG. 5B provides a diagram of the case in which two different devices,Information Source Device and Information Source Device 2 each send aninformation element to a Monitored Host, wherein both informationelements are relayed by a Relay Device.

DETAILED DESCRIPTION OF THE INVENTION

Prior to setting forth the invention, it may be helpful to anunderstanding thereof to first set forth definitions of certain termsthat are used hereinafter.

As used herein the term “communication” refers to the transfer of atleast one information element between two devices. For example, an IPpacket transferred over the Internet from one device to another deviceis a communication. In another example, an HTTP request transferred froman HTTP client to an HTTP server over the Internet is a communication.It should be noted that one or more communications could be transferredin one or more other communications. A group of communications in whichone communication contains the other is called a ‘Protocol Stack’. Forexample, a communication in the HTTP protocol (i.e. an HTTP request orresponse) is normally contained in a communication in the TCP protocol(i.e. a TCP connection), which is in turn contained in a communicationin the IP protocol (i.e. one or more IP datagrams).

As used herein the term “original source of an information element”refers to the device that sent that information element, but has notrelayed that information element from another device.

As used herein the term “transmitter” refers to a device that sent aninformation element, including in cases where the information elementwas previously relayed from another device. When an information elementis received from a device, that device is a transmitter of thatinformation element.

As used herein the term “feature” refers to any information about adevice that may be different between two different devices.

Embodiments of the present invention recite the receiving and/or thesending of “information elements” over a data network. In someembodiments, information elements are communicated using a communicationprotocol. Exemplary communication protocols for communicated informationelements over a data network include but are not limited to HTTP, SMTP,DNS (see RFC 1034), SSL/TLS (see RFC 2246), TCP, UDP (see RFC 768), IP,and ICMP (see RFC 792).

FIG. 1 provides an illustration of an environment in which a RelayDetection System 102 operates according to some embodiments of thepresent invention. In some embodiments, Relay Detection System 102 (RDS)receives information elements communicated from an Information SourceDevice 104 (ISD) over the Internet 100.

In some instances, in order to send information elements to a MonitoredHost 110 (MH), an ISD 104 first sends information elements to a RelayDevice 108 (RD), which receives the information elements andsubsequently relays the received information elements to the MH 110. Forthese instances, the relayed information elements travel from theInformation Source Device 104 to the Monitored Host 110 as denoted bypath 122.

Alternately, the ISD 104 does not use the Relay Device 108, and sendsthe information elements to the Monitored Host 110 without traversingthe RD 108, as denoted by path 120.

It is desired to ascertain whether or not information elements sent tothe MH 110 are sent through an RD 108.

The present inventors have devised methods, apparatus and computerreadable software for determining whether information elements sent toMH 110 were sent via an RD 108. In some embodiments, the determining isperformed by RDS 102, which monitors at least one communication receivedby the MH 110 and attempts to determine whether a communication is sentto the MH 110 using RD 108. As used herein the term ‘monitor’ refers tothe act of receiving communications, including in cases where thecommunications were sent from or to the device that is performing themonitoring.

Any class of relay devices is appropriate for the present invention.Examples of classes of relay devices include but are not limited toSOCKS Proxies (see RFC 1928), HTTP Proxies used with the GET method (seeRFC 2616), HTTP Proxies used with the CONNECT method (see RFC 2817), IPRouters (see RFC 1812), and NAT devices (see RFC 2663).

ISD 104 is a device configured to communicate with other devices overany data network, such as Internet 100. In some embodiments, ISD 104 isa device operated by a person or group of persons. In some embodiments,ISD 104 is a device operating automatically. In some embodiments, ISD104 is a device operating automatically in a manner that simulates theactions of a person. Exemplary ISDs include but are not limited to acomputer running an HTML browser such as Microsoft Internet Explorer(for an explanation of HTML see the HTML Specification in the W3Cwebsite at http://www.w3.org/TR/html), a computer running an IRC client,a computer running an SMTP client, and a cellular phone running an XHTMLbrowser. MH 110 is a device configured to communicate with other devicesover any data network, such as Internet 100. In one exemplaryembodiment, Monitored Host 110 is a server. Examples of appropriateMonitored Hosts 110 include but are not limited to an HTTP server, aSSL/TLS server, an SMTP server, a file server, a telnet server, an FTPserver, an SSH server, a DNS server, and an IRC server. Examples of usesof MH 110 include but are not limited to hosting an online merchant,running an online advertising service, and receiving email.

In some embodiments, RDS 102 monitors information elements sent fromand/or to the MH 110. Optionally, RDS 102 is further configured tocommunicate with the RD 108 and/or the ISD 104. Optionally, the RDS 102is further configured to monitor information elements sent from and/orto the RDS 102.

Each of the RDS 102, ISD 104, RD 108, and MH 110 may be hardware,software or a combination thereof, may reside at the same or atdifferent geographical locations, or may be components of the samedevice.

For simplicity reasons, the presented environment contains oneinformation source device, and one relay device. In practice, there aremany information source devices connected to the Internet 100, and eachof them may or may not use one of several relay devices that are alsoconnected to the Internet 100. The goal of the present invention is todifferentiate between the general case of an information source devicethat does not use a relay device, and the general case of an informationsource device that does use a relay device. It will be appreciated thatthe extrapolation from the presented environment to real-lifeenvironments such as the Internet or other networks is well within thescope of the skilled artisan.

Referring to FIG. 2A, it is noted that according to some embodiments ofthe present invention, the RDS 102 receives information elements sent tothe MH 110, wherein a Potential Relay Device 150 (PRD) is a transmitterof the information elements, but is not necessarily the original sourceof each or any of the information elements. According to someembodiments, the identity of Potential Relay Device 150 (PRD) is unknownand may be either RD 108, or ISD 104.

Some embodiments of the present invention provide methods, apparatus andcomputer readable software for determining whether PRD 150 is RD 108 orISD 104.

FIG. 2B provides a diagram of the original sources of informationelements received by RDS 102 according to some embodiments of thepresent invention. A first information element and a second informationelement are received by RDS 102. According to some embodiments, PRD 150is the original source of the second information element, and thus thesecond information element may also be referred to as a Non-RelayedInformation Element (NRIE). In contrast, ISD 104 is the original sourceof the first information element, and thus the first information elementmay also be referred to as a Potentially Relayed Information Element(PRIE). Therefore, in the case where PRD 150 is ISD 104 then PRD 150 isthe original source of the PRIE, and in the case where PRD 150 is RD 108then PRD 150 is not the original source of PRIE.

In particular embodiments, the NRIE is of a type not relayed by aspecific class of relay devices, thus ensuring that the secondinformation element is not actually relayed by a relay device of thatclass. For example, a standard HTTP Proxy (either using the CONNECT orthe GET methods) does not relay ICMP messages. Therefore, if RD 108 is aproxy of that type and RD 108 is a transmitter of an ICMP message, thenthe ICMP message can be assumed to be an NRIE.

According to some embodiments of the present invention, it is determinedwhether a feature of ISD 104 and a feature of PRD 150 are features thatare unlikely to relate to the same device (Incompatible Features). Afeature is said to relate to a device if the feature is informationabout that specific device.

In some embodiments, the feature of ISD 104 is derived from the contentof the PRIE. In alternate embodiments, the feature of ISD 104 is derivedfrom other characteristics described below. In some embodiments, thefeature of PRD 150 is derived from the content of the NRIE. In alternateembodiments, the feature of PRD 150 is derived from othercharacteristics described below.

It is also noted that it is not a requirement of the present inventionto actually obtain either a feature of PRD 150 or a feature of ISD 104.In some embodiments detailed below, the RDS 102 can determine whether ornot the features are Incompatible Features, without discovering each orany of the features. The presence of Incompatible Features increases thelikelihood that ISD 104 and PRD 150 are distinct devices (i.e. PRD 150is RD 108), while the absence of Incompatible Features increases thelikelihood that PRD 150 and ISD 104 are the same device (i.e. PRD 150 isnot RD 108).

FIG. 2C provides a diagram of the case wherein PRD 150 is ISD 104. Inthis case, it is detected that the original source of the firstinformation element (ISD 104) is the same device as the original sourceof the second information element (PRD 150), and it may therefore beconcluded that the Potential Relay Device 150 is the ISD 104 and NOT aRelay Device 108, and it may also be concluded that PRIE was not relayedby the Relay Device 108.

FIG. 2D provides a diagram of the alternate case wherein PRD 150 and ISD104 are distinct devices. In this case, it is detected that the originalsource of the first information element (ISD 104) is a different devicethan the original source of the second information element (PRD 150).Thus, since PRIE has an original source that is not PRD 150, it isconcluded that PRIE has been relayed by PRD 150, and that therefore PRD150 is a Relay Device 108.

As used herein, the term “feature” refers to at least one feature. Thus,it is disclosed that a combination of more than one feature is definedas a feature in and of itself.

As used herein, an “ISD-Feature” is a feature of the original source ofthe first information element (i.e. the source of the PRIE, which is ISD104), while a “PRD-Feature” is a feature of the source of the secondinformation element (i.e. the source of the NRIE, which is PRD 150).Examples of ISD-Features, PRD-Features, methods of discovering thesefeatures, and the way in which these features can be used to determinewhether ISD 104 is a different device than PRD 150 are given below.

As stated above, one option for ensuring that the NRIE was not relayedby RD 108 is to select the NRIE to be of an information element typeknown not to be relayed by relay device of the specific class of relaydevices to which RD 108 belongs. For example, it is known that certainSOCKS proxies relay HTTP communications but do not relay TCPcommunications. If RD 108 is a SOCKS proxy it will maintain one TCPconnection with ISD 104 and another separate TCP connection with MH 110,and will relay HTTP communications from one TCP connection to the other.Thus, in some embodiments, the PRIE is part of a possibly relayed HTTPcommunication, and the NRIE is part of a non-relayed TCP communication.

In some embodiments, the first and second information elements (NRIE andPRIE) are part of two different layers on a Protocol Stack of a singlecommunication. Thus, in one particular case a single HTTP over TCPcommunication is sent, and the first non-relayed information element ispart of the TCP layer of the communication, while the second possiblyrelayed information element is part of the HTTP layer of thecommunication. Alternately, the first and second elements are parts oftwo separate communications.

Sometimes, however, the class of the Relay Device 108 is not necessarilyknown to the Relay Detection System 102. In some embodiments, thedisclosed method explicitly requires an optional step of estimating ortargeting a specific class of relay devices, and performing the methodunder the assumption that a potential class of relay devices is of thattargeted class of relay devices.

In some embodiments, methods of the present invention are repeated fordifferent pairs of NRIE and PRIE, wherein each pair is instrumental indetecting at least one class of relay devices.

In general, it is disclosed that in some embodiments, a disclosed methodmay repeated sequentially or in parallel a number of times, wherein afinal likelihood that a potential relay device is a relay device isderived from some sort of aggregate of results from the repeatedmethods. In some embodiments, obtaining an aggregate includes obtainingan average, a weighted average, a minimum, maximum or any other methodof characterizing aggregate results known in the art.

Using Communication Latency

In one particular embodiment of the present invention, ISD-Feature ischosen to be the latency of communications between ISD 104 and MH 110,and PRD-Feature is the latency of communications between PRD 150 and MH110. Since the latency from one device to another device is usuallyrelatively stable, then the same device is not likely to exhibit twosignificantly different latencies. Therefore, if the ISD 104 latency andthe PRD 150 latency are significantly different, then it is relativelymore likely that PRD 150 and ISD 104 are distinct devices (i.e. PRD 150is a Relay Device 108, and PRIE was being relayed). Similarly, if theISD 104 latency and the PRD 150 latency are similar, then it isrelatively more likely that PRD 150 and ISD 104 are the same device(i.e. PRIE was not being relayed).

As used herein the term ‘latency’ refers to the time delay between thesending of a communication and its receipt.

Latency occurs because of various reasons. One reason is the timerequired for electric signals or electromagnetic waves to travel thedistance between two points on the path of the communication (e.g.electric signals in an electric cable, light in an optical fiber, ormicrowaves in a microwave-link). Another reason is the time required forinformation to be transferred over a communication line (e.g. it wouldtake 25 milliseconds (ms) for 1500 Bytes to be fully transferred over a480 kilobits-per-second (kbps) communication line). Another reason isthe store-and-forward method used in many data networks, whereinportions of the communications (e.g. packets or cells) are forwardedfrom one intermediate network element to the next, only after they havebeen received in full. Another reason is the delaying of communicationsin buffers of switching elements in the network (e.g. when acommunication line is in the process of transferring one communication,new communications are saved in a buffer until the line is freed up).Another reason is the processing time of certain communications, such asfor making routing decisions, encryption, decryption, compression ordecompression.

Since a communication is sent from one device and received at adifferent device, it is usually easier to measure RoundTrip Time (RTT)rather than latency. RTT is the time passed between the sending of anoutgoing communication (OC) from MH 110 and the receipt of an incomingcommunication by MH 110 (IC), which was sent immediately upon receipt ofOC. RTT is therefore the sum of the latency of the OC and the latency ofthe IC. For example, when using the ICMP echo mechanism (see RFC 792),RTT is the time passed between sending the Echo message and receivingthe Echo Reply message.

FIG. 4A describes the latencies of communications between ISD 104 and MH110 in the case where RD 108 is being used.

T1 is the latency of communications from MH 110 to RD 108

T2 is the latency of communications from RD 108 to ISD 104.

T3 is the latency of communications from ISD 104 to RD 108.

T4 is the latency of communications from RD 108 to MH 110.

FIG. 4B describes the latencies of communications between ISD 104 and MH110 in the case where RD 108 is not being used.

T5 is the latency of communications from MH 110 to ISD 104.

T6 is the latency of communications from ISD 104 to MH 110.

As used herein the term “ISD RTT” refers to the round-trip time ofcommunications between MH 110 and ISD 104.

As used herein the term “PRD RTT” refers to the round-trip time ofcommunications between MH 110 and PRD 150.

As used herein the term “RTT gap” refers to the difference between ISDRTT and PRD RTT.

In the case where PRD 150 is RD 108 (i.e. PRIE is relayed) theround-trip time of ISD RTT should be longer than the PRD RTT.Specifically, PRD RTT is equal to T1+T4 (the RTT between MH 110 and RD108), and ISD RTT is equal to T1+T2+T3+T4 (the RTT between MH 110 and RD108 plus the RTT between RD 108 and ISD 104). The RTT gap equals to theRTT between PRD 150 (which is RD 108) and ISD 104, which is equal toT2+T3.

However, in the case where PRD 150 is ISD 104 (i.e. PRIE is not relayed)then ISD RTT and PRD RTT are both equal to T5+T6 (the RTT between MH 110and ISD 104). The RTT gap should therefore be close to zero.

For example, if ISD RTT is 640 milliseconds and PRD RTT is 130milliseconds, it is more likely that PRD 150 is Relay Device 108 andthat PRIE is being relayed than if ISD RTT is 133 milliseconds and PRDRTT is 130 milliseconds.

It should be noted that even in the case where PRD 150 is ISD 104 somedifferences between ISD RTT and PRD RTT might be found, due to differentnetwork delays that each communication was subject to. However, in mostpractical cases the RTT gap when using a relay device is noticeablylarger than the RTT gap When not using a relay device.

When measuring the RTT gap the RDS 102 is effectively performing twofeature comparisons. The first is the comparison of the latency of acommunication from ISD 104 to MH 110 compared to the latency of acommunication from PRD 150 to MH 110. The second is the comparison ofthe latency of a communication from MH 110 to ISD 104 110 compared tothe latency of a communication from MH 110 to PRD 150. Both latenciesshould be larger in relayed communications compared to non-relayedcommunications, meaning that the RTT gap, which is the sum of twolatency differences, should also be larger in relayed communicationscompared to non-relayed communications.

In an exemplary embodiment RD 108 is a SOCKS proxy, ISD 104 is an HTTPclient and MH 110 is an HTTP server. In this case, RDS 102 obtains theISD RTT by measuring the RTT of an HTTP communication (a PRIE), andobtains the PRD RTT by measuring the RTT of a TCP communication (anNRIE).

In another exemplary embodiment RD 108 is an HTTP proxy using theCONNECT method, ISD 104 is an SMTP client, and MH 110 is an SMTP server.In this case, RDS 102 obtains the ISD RTT by measuring the RTT of anSMTP communication (a PRIE). RDS 102 then sends an ICMP Echo message tothe source IP address of the TCP connection (an NRIE) in which the SMTPcommunication was received. RDS 102 then receives an ICMP Echo Replymessage. The PRD RTT is the time between the two ICMP messages (asexplained below the original source of the ICMP Echo Reply message isPRD 150).

Methods for measuring the RTT of various types of communications aredescribed below.

The RTT gap is also useful in differentiating between various uses ofrelay devices. For performance and security reasons, legitimate usersnormally use a near-by relay device (e.g. on the same corporatenetwork), resulting in a short RTT gap. On the other hand, malicioususers often use a remote relay device (e.g. in another country),resulting in a long RTT gap. A long RTT gap is therefore indicative of arelay device used for malicious purposes. This method is especiallyeffective in cases where malicious users cannot avoid using a remoterelay device. For example, an Indonesian fraudster wishing to appear asif he is located in the USA must use a remote relay device. In anotherexample, it would be significantly more difficult for a spammer to use alarge number of relays if all of them must have short RTT gaps.

Measuring RTT

Accurate RTT measurements require that IC be sent immediately uponreceipt of the OC. This may be achieved in several ways.

Some protocol implementations provide immediate response on somecommunications. For example, in a TCP three-way handshake a segmentcontaining the SYN and ACK control flags (SYN-ACK segment) should besent immediately upon receipt of the related segment containing the SYNcontrol flag (SYN segment). The RTT in such a case is the time betweensending of a SYN segment (OC) and receipt of a SYN-ACK segment (IC).

In other cases, the protocol implementation might not provide animmediate response, but an application handling the communications couldbe expected to generate it. For example, an HTTP client would normallygenerate an HTTP request immediately upon receiving an HTTP ‘302’response. In another example, an HTML browser would normally generate anHTTP request immediately upon receiving the first embedded image in anHTML page (e.g. using the HTML <img> tag). In another example, anSSL/TLS layer will send a ClientHello message immediately upon receivingthe TCP SYN-ACK segment indicating the TCP connection was established.In another example, an SMTP client would normally send a ‘RCPT’ commandimmediately upon receiving a ‘250’ response to a previous ‘MAIL’ command(see RFC 821). In another example, an IRC client would normally send a‘PONG’ message immediately upon receiving a ‘PING’ message from an IRCserver.

In other cases, human interaction could be used to generate immediateresponses. For example, a user is presented with a game in which heshould press a keyboard key immediately upon seeing a signal on thescreen. The signal is presented when OC is received, and IC is sent whenthe user responds.

Several RTT measurements taken over a short period of time may producedifferent results. This is due to variations in network congestions andother parameters. It is therefore recommended to make several RTTmeasurements if possible. Furthermore, since the RTT cannot fall belowthe time if takes for the electric or electro-magnetic signal to travelthe complete route, using the lowest of several RTT measurements willnormally produce more accurate and reliable results.

It should be noted that a malevolent user may send an IC prior toreceiving an OC. This will deceive RDS 102 to calculate a shorter RTT.It is therefore recommended to place some secret information in OC(secret information is information that cannot be easily obtained by aperson or device that does not already know the secret), and requirethat IC contain the secret information (or a derivative of it). Thisprevents the sending of an IC before receiving the secret information inOC. For example, the HTTP ‘302’ response described above may redirectthe HTTP client to a URL that contains a secret. The HTTP client wouldthen generate an HTTP request to that URL, thereby sending the samesecret back. In another example, a TCP SYN-ACK segment (an OC) containsa secret Initial Sequence Number, and a TCP segment containing the ACKcontrol flag (TCP ACK segment; an IC) contains an AcknowledgementNumber, which is a derivative of the Initial Sequence Number. In anotherexample, an ICMP Echo message (an OC) contains a secret Identifier,Sequence Number or Data, and an ICMP Echo Reply message (an IC) containsthe same secret.

It should be noted that when calculating an RTT RDS 102 must alsomonitor communications sent by MH 110 (and not only communicationsreceived by MH 110), in order to detect the time at which each OC issent. However, this requirement may be bypassed if an OC to ISD 104 andan OC to PRD 150 are known to be sent at the same time. In such a case,the RTTs are unknown, but the RTT gap may still be calculated, and isequal to the difference between the times of arrival of the respectiveIC's. For example, if PRIE is SSL/TLS and NRIE is TCP, the TCP SYN-ACKsegment sent by MH 110 is such an OC, and the RTT gap is the timebetween receipt of the corresponding TCP ACK segment and receipt of theSSL/TLS ClientHello message.

If MH 110 does not send an OC, which can be used by RDS 102, RDS 102 mayneed to send such an OC by itself. For example, RDS 102 is monitoringHTTP communications to and from a website (MH 110). In order to measurethe RTT of the PRIE, RDS 102 provides an HTTP ‘302’ response for some ofthe HTTP requests received by MH 110, as described above. In thisexample RDS 102 may need to be a software module installed on MH 110, soit could respond to HTTP communications sent to MH 110.

In the embodiments involving measurements of latency or RTT it isrecommended to check that ISD RTT is ‘significantly different’ than PRDRTT. The RTTs are significantly different when the difference betweenthem is one that rarely occurs when making RTT measurements oncommunications with the same device. At the time of writing of thistext, the RTT between two devices in a reasonably stable Internetenvironment does not vary by more than 50 milliseconds within a timeframe of a few seconds. In contrast, the RTT gap in relayedcommunications usually exceeds 100 milliseconds. Therefore, in someembodiments, ‘significantly different’ can be interpreted to mean ‘morethan 60 milliseconds’. In some embodiments, ‘significantly different’can be interpreted to mean ‘more than 80 milliseconds’. In someembodiments, significantly different' can be interpreted to mean ‘morethan 100 milliseconds’, and so forth.

In some embodiments, the RTT to a device is not directly measured butrather estimated based on other information known about the device, suchas its geographical location, its IP address' reverse DNS record (i.e.host address to host name translation), and/or its IP address' WHOISrecord (for information about the WHOIS service see the AmericanRegistry for Internet Numbers website at http://www.arin.net). Forexample, if MR 110 is located in New York City, N.Y., USA and an IPgeo-location service indicates that PRD 150 is located in Los Angeles,Calif., USA and the text ‘dsl’ is found in the reverse DNS record of thePRD 150's IP address indicating it is likely a Digital Subscriber Line(DSL; for information about DSL see the DSL Forum website athttp://www.dslforum.org), then RDS 102 can estimate that the RTT betweenMR 110 and PRD 150 is in the range of 65-85 milliseconds. This isbecause it is known that the RTT on the Internet between New York Cityand Los Angeles is usually approximately 55 milliseconds, and because itis known that a DSL usually adds an additional 10-30 milliseconds to theRTT.

Using Device Configuration Status

In another particular embodiment of the present invention, ISD-Featureand PRD-Feature are the configuration status of the ISD 104 and PRD 150,respectively. As used herein, the term ‘configuration status’ refers tothe hardware and software of a device and the way they are customized.

If ISD-Feature and PRD-Feature are configuration statuses that areunlikely to relate to the same device, then it is relatively more likelythat PRD 150 and ISD 104 are distinct devices (i.e. PRD 150 is a RelayDevice 108, and PRIE was being relayed).

Similarly, if ISD-Feature and PRD-Feature are configuration statusesthat are likely to relate to the same device, then it is relatively morelikely that PRD 150 and ISD 104 are the same device (i.e. PRIE was notbeing relayed).

There are several known methods of detecting a device's configurationstatus from communications. One method is to use explicit configurationinformation provided by the device in the communication. For example,HTTP clients normally include in each HTTP request the header‘User-Agent’ which provides information on the operating system type andversion, the HTTP client type and version, and additional softwareinstalled on the device. Email applications may provide similarinformation in the RFC 822 ‘X-Mailer’ header, email servers may providesuch information in the RFC 822 ‘Received’ header, and HTTP serversnormally include in an HTTP response the header ‘Server’ which providesinformation on the HTTP server type and version.

Another method is to deduce the device's configuration status from themanner it implements various communication protocols. The popularnetwork administration tool ‘Nmap’ includes many implementations of thismethod, as described in detail in the article ‘Remote OS detection viaTCP/IP Stack Fingerprinting’ written by the developer of Nmap (availableat http://www.insecure.org/nmap/nmap-fingerprinting-article.html). Forexample, the article suggests examining the Initial Window chosen by aTCP implementation, since different operating systems choose differentnumbers. It should be noted that while the article assumes that theinvestigated device is responding to a communication, this method isalso applicable to communications initiated by a device (although thespecific indications may vary).

In an example of this embodiment, where RD 108 is a SOCKS proxy, the RDS102 monitors an HTTP request (PRIE) that includes the header‘User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)’—Thisheader indicates the operating system is Microsoft Windows 2000. TheHTTP request is sent over a TCP connection (NRIE) that had an InitialWindow of 5840—This is typical of other operating systems (specificallyRed Hat Enterprise Linux). Since one device could not concurrently runtwo operating systems, then RDS 102 determines that ISD 104 and PRD 150are distinct devices (i.e. PRD 150 is a Relay Device 108, and the HTTPrequest was being relayed). In this example, ISD-Feature is theinformation that ISD 104 is running a Microsoft Windows 2000 operatingsystem, and PRD-Feature is the information that PRD 150 is running a RedHat Enterprise Linux operating system.

In another example of this embodiment, where RD 108 is a HTTP proxyusing the CONNECT method, the RDS 102 monitors an HTTP request (PRIE)that includes the header ‘Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en)AppleWebKit/124 (KHTML, like Gecko) Safari/125’—This header indicatesthe operating system is Apple Mac OS X. The HTTP request is sent over aTCP connection (NRIE). RDS 102 connects to port 80 of the source IPaddress of the TCP connection and sends an HTTP request. RDS 102 thenreceives an HTTP response containing the header ‘Server:Microsoft-IIS/5.0’ (as explained below the original source of this HTTPresponse is PRD 150). Since it is known that Microsoft IIS servers donot run on the Apple Mac OS X operating system, then RDS 102 determinesthat ISD 104 and PRD 150 are distinct devices (i.e. PRD 150 is a RelayDevice 108 and the HTTP request from ISD 104 was being relayed). In thisexample, ISD-Feature is the information that ISD 104 is running an AppleMac OS X operating system, and PRD-Feature is the information that PRD150 is running a Microsoft IIS server.

In some cases it is necessary to send to the original source of aninformation element an OC that will cause the original source to sendback an IC that could be used to determine its configuration. In theexample given above where the HTTP ‘Server’ header is used, the HTTPrequest sent from RDS 102 to PRD 150 is an OC and the HTTP response isan IC. Methods of ensuring that an OC is sent to the original source ofan information element, and methods of ensuring that an IC is receivedfrom the original source of an information element are disclosed below.

Using Location, Sub-network or Administrator Information

In another particular embodiment of the present invention, ISD-Featureand PRD-Feature are the location, sub-network and/or administrator ofthe ISD 104 and PRD 150, respectively. As used herein, the term‘location’ refers to the geographic location of a device, the term‘sub-network’ refers to the group of devices that is close to a devicein the network topology, and the term ‘administrator’ refers to theorganization that connects the device to the network (e.g. to theInternet). Examples of a device's location could be ‘New York City,N.Y., United States of America or ‘Longitude 32 degrees 5 minutes North,Latitude 34 degrees 46 minutes East’ . Examples of a device'ssub-network could be ‘all devices on the same local area network segmentas the device whose IP address is 1.2.3.4’ . Examples of a device'sadministrator could be ‘Earthlink, Inc. of Atlanta, Ga., USA’, which isan Internet Service Provider that connects users to the Internet for afee, or ‘General Electric Company of Princeton, N.J., USA’, which is acompany that connects some of its employees to the Internet as requiredfor their work.

A single device is not likely to concurrently have two differentlocations, sub-networks or administrators. Therefore, if ISD 104 isfound to be in a different location and/or on a different sub-networkand/or has a different administrator than PRD 150, then it is relativelymore likely that ISD 104 and PRD 150 are distinct devices (i.e. PRIE wasbeing relayed). Similarly, if ISD 104 and PRD 150 are found to be in thesame location and/or on the same sub-network and/or have the sameadministrator have, then it is relatively more likely that PRD 150 andISD 104 are the same device (i.e. PRIE was not being relayed).

In an exemplary embodiment RD 108 is a SOCKS proxy, ISD 104 is an SMTPclient and MH 110 is an SMTP server. In this case, RDS 102 uses thesource IP address of the TCP session (an NRIE) and an IP geo-locationservice to estimate the location of the PRD 150. It then uses an RFC 822‘Date’ header reported in the SMTP communication (a PRIE) to estimatethe location of ISD 104. The ‘Date’ header indicates the time (‘wallclock’) and time zone configuration of the ISD 104, and is therefore anindication of its location (since devices are normally configured to thelocal time and time zone). If the two locations do not match (e.g. thegeo-location service indicates that PRD 150 is located in New York City,while the ISD 104's time zone is GMT+7), then RDS 102 determines thatPRD 150 and ISD 150 are distinct devices (i.e. PRD 150 is a Relay Device108 and the SMTP communication was being relayed).

Alternative methods of estimating the location of PRD 150 (other thanusing an IP geo-location service) include but are not limited to: (a)Checking the IP address's WHOIS record. The address given in the WHOISrecord is likely relatively close to the location of PRD 150; and (b)Checking the IP address's reverse DNS record (e.g. if the record endswith ‘.fr’ then PRD 150 is likely in France).

Alternative methods of estimating the location of ISD 104 (other thanusing the ‘Date’ header in an SMTP communication) include but are notlimited to: (a) (in case PRIE is SMTP) checking the last RFC 822‘Received’ header reported in the SMTP communication, which shouldcontain the time zone configuration of the SMTP server used by ISD 104,which is often the same as the time zone of the ISD 104 itself; (b) (incase PRIE is HTTP) checking the HTTP header ‘Accept-Language’, whichindicate the languages supported by ISD 104 (e.g. the header“Accept-Language: ru” means ISD 104 supports content in the Russianlanguage, and it is therefore relatively more likely that ISD 104 islocated in Russia); and (c) checking the location of the source ofanother communication which was triggered by an event at the ISD 104 (anISD Triggered Communication), as described in detail below, using any ofthe methods described above for estimating the location of PRD 150.

In another exemplary embodiment RD 108 belongs to a class of relaydevices that do not relay TCP (i.e. TCP is a NRIE) and RDS 102 uses thesource IP address of a TCP session to estimate the sub-network of PRD150. This may be done by retrieving the WHOIS record, reverse DNS recordor routing database record associated with that IP address (forinformation about routing databases see the RADb website athttp://www.radb.net). This may also be done by discovering routersadjacent to PRD 150 using ‘Time Exceeded’ ICMP messages sent in responseto IP packets with small Time-to-Live values, as done by the Unixutility traceroute (or the equivalent Microsoft Windows utilitytracert), since devices in the same sub-network normally connect to theInternet 100 through the same routers. RDS 102 then estimates thesub-network of the ISD 104. This may be done by checking the sub-networkof the source of an ISD Triggered Communication, as described in detailbelow, using any of the methods described above for estimating thesub-network of PRD 150. If the two sub-networks do not match (e.g. thesub-network names in the devices' WHOIS records are different or thedevices do not have a common adjacent router), then RDS 102 determinesthat PRD 150 and ISD 150 are distinct devices (i.e. PRD 150 is a RelayDevice 108 and the PRIE was being relayed).

In another exemplary embodiment wherein RD 108 belongs to a class ofrelay devices that do not relay TCP (i.e. TCP is a NRIE) and RDS 102uses the source IP address of a TCP session to estimate theadministrator of PRD 150. Exemplary methods for estimating theadministrator include but are not limited to: (a) Retrieving the WHOISrecord associated with that IP address (the organization name given inthe record is likely the administrator); (b) Retrieving the reverse DNSrecord associated with that IP address (e.g. if the record ends with‘cox.net’ then the administrator is likely ‘Cox Communications ofAtlanta, Ga., USA); (c) Retrieving the WHOIS record associated with thesecond-level domain in the reverse DNS record associated with that IPaddress; and (d) Retrieving the routing database record associated withthat IP address. RDS 102 then estimates the administrator of ISD 104.Methods for estimating the administrator of ISD 104 include but are notlimited to: (a) (in case PRIE is HTTP) checking the HTTP header‘User-Agent’ which sometimes contains information about theadministrator. For example, a ‘User-Agent’ header containing the text‘AOL 9.0’ indicates the HTML browser installed on ISD 104 was providedby America Online, Inc. of Dulles, Va., USA (AOL). Since many Internetusers receive their HTML browser from the same organization throughwhich they connect to the Internet, this increases the likelihood thatISD 104 connects to the Internet through AOL (i.e. AOL is theadministrator). In another example, the text ‘Cox High Speed InternetCustomer’ indicates the browser was provided by Cox Communications, Inc.of Atlanta, Ga., USA; (b) (in case PRIE is SMTP) checking the RFC 822‘Organization’ header, which sometimes contains information about theadministrator; and (c) checking the administrator of the source IPaddress of an ISD Triggered Communication, as described in detail below,using any of the methods described above for estimating theadministrator of PRD 150.

ISD Triggered Communications

Information about ISD 104 may be discovered by triggering ISD 104 tosend communications. Such a communication is an ‘ISD TriggeredCommunication’.

Exemplary ISD Triggered Communications that expose the IP address of ISD104 are disclosed in PCT Application WO02/08853, the entirety of whichis herein incorporated by reference. After receiving the ISD 104's IPaddress, RDS 102 may use the methods described above to find itslocation, sub-network or administrator. It can then compare them to thelocation, sub-network or administrator of the PRD 150, and determinewhether they are different devices. Alternatively, RDS 102 can comparethe ISD 104's IP address to the PRD 150's IP address directly. If theyare different, it is relatively more likely that ISD 104 is a differentdevice than PRD 150 (i.e. PRD 150 is a Relay Device 108, and PRIE wasbeing relayed).

Another exemplary triggered communication is a DNS request. In somecases, ISD 104 will send a DNS request associated with a PRIE in orderto translate a hostname into an IP address. The ISD 104 will send theDNS request to the DNS server(s) that it is configured to use. The ISD104's DNS server will then send a DNS request to the authoritative DNSserver for the given hostname. RDS 102 monitors DNS requests sent tothis authoritative DNS server. It should be noted that although the DNSrequest that RDS 102 monitors may be received from DNS server that ISD104 is configured to use, ISD 104 is the original source of at least oneinformation element contained in the DNS request. US Patent applicationUS2002016831, the entirety of which is herein incorporated by referencedescribes methods of causing a device to generate DNS requests, as wellas methods of associating the DNS requests with the identity of thedevice that originated them. One method to associate a DNS request withthe relevant PRIE is to configure the authoritative DNS server to replywith a different IP address to each request for translation of ahostname, and to keep a record of which DNS request received which IPaddress as a reply. When the PRIE is received at one of the IPaddresses, the associated DNS request can be retrieved from the record.

After receiving the DNS Request from the ISD 104's DNS server, RDS 102may use the methods described above to find its location, sub-network oradministrator. For performance and economical reasons, many devicesconnected to the Internet are configured to use a DNS server that is ina similar location, on the same sub-network, or administered by the sameadministrator. RDS 102 can therefore compare the location, sub-networkor administrator of the PRD 150, to the location, sub-network oradministrator of the ISD 104's DNS server, respectively. If they do notmatch, it is relatively more likely that PRD 150 is a different devicethan ISD 104 (i.e. PRIE is being relayed).

Using Maximum Communication Rate

In another particular embodiment of the present invention, the maximumcommunication rate (MCR) of the PRD 150 and ISD 104 are used todetermine whether they are the same device. The term MCR refers to themaximum amount of information a device can receive (incoming MCR) orsend (outgoing MCR) during a time interval. ‘Bits per Second’ (bps) is acommon measure of MCR. For example, some DSL lines have an incoming MCRof 1.5 Million bps (Mbps), and an outgoing MCR of 96 thousand bps(kbps).

If the MCR of the PRD 150 is different than that of the ISD 104 then itis more likely that ISD 104 is a different device than PRD 150 (i.e.PRIE is being relayed).

In an example of this embodiment, RD 108 is connected to the Internet100 on a DSL line with a 1.5 Mbps incoming MCR and a 96 kbps outgoingMCR. Since relayed communication from MH 110 to ISD 104 are transferredthrough the incoming interface of RD 108 and then through its outgoinginterface, then the incoming MCR of the ISD 104 could not exceed theoutgoing MCR of RD 108 (96 kbps). Therefore, PRD 150's incoming MCR is1.5 Mbps while ISD 104's incoming MCR is 96 kbps or less.

In another example of this embodiment, RD 108 is connected to theInternet 100 at an MCR of 20 Mbps in both directions, and ISD 104 isconnected to the Internet 100 on a DSL line with a 1.5 Mbps incoming MCRand a 96 kbps outgoing MCR. Therefore, PRD 150's incoming MCR is 20 Mbpswhile ISD 104's incoming MCR is 1.5 Mbps, and PRD 150's outgoing MCR is20 Mbps while ISD 104's outgoing MCR is 96 kbps.

Detecting MCR

According to some embodiments of the present invention, checking whetherthe MCR of ISD 104 is different than the MCR of PRD 150 is done bydetecting the MCR of each and comparing them. One method of detecting anMCR is sending information to, or receiving information from, a device,using a protocol that automatically adjusts to the maximum communicationrate possible, such as TCP, and observing the communication rate. For anexplanation of some of the mechanisms used in TCP for adjusting to theMCR, see the article ‘JACOBSON, V. Congestion avoidance and control. InProceedings of SIGCOMM '88 (Stanford, Calif., August 1988), ACM’ and thearticles it references.

Another method of observing the incoming communication rate of a deviceinvolves monitoring receipt acknowledgements received from the device.For example, a device receiving information on a TCP connection sendsfrom time to time the amount of information it has successfullyreceived. Receiving an acknowledgement of byte number 3,000,000 at onetime and an acknowledgement of byte number 3,250,000 twenty secondslater, would indicate that the device is receiving information at a rateof 12,500 Bytes per Second, which equals 100,000 Bits per Second (i.e.its incoming MCR is 100 kbps). In another example, as described above,an HTML browser would normally generate an HTTP request immediately uponreceiving the first embedded image in an HTML page (e.g. using the HTML<img> tag). Receiving the HTTP request forty seconds after starting tosend an HTML page in which the embedded image tag is located at offset1,000,000 bytes, would indicate that the device is receiving informationat a rate of 25,000 Bytes per Second, which equals 200,000 Bits perSecond (i.e. its incoming MCR is 200 kbps). It should be noted that thismeasurement might be inaccurate since it compares the sending of thebeginning of the HTML page to the receipt of the HTTP request, therebyadding at least one round trip time to the measurement. Measuring theround trip time and subtracting it from this time measurement mayproduce more accurate results.

RD 108 normally buffers relayed communications between MH 110 and ISD104. Buffers are temporary storage into which RD 108 writescommunications it receives, and from which RD 108 reads thecommunications it sends. When the buffers are not full, RD 108 canreceive communications in its incoming MCR rate. When the buffers arefull, RD 108 can receive communications at the rate it can empty thebuffers (i.e. at the rate it can send communications out from thebuffers). This means that a measurement of the communication rate fromMH 110 to RD 108 would be an indication of RD 108's incoming MCR whenthe buffers are not full, and an indication of ISD 104's incoming MCRwhen the buffers become full. The buffers would become full if ISD 104'sincoming MCR is smaller than RD 108's incoming MCR. For example, if RD108 has buffers of size 100,000 bytes, and its incoming MCR is 1.5 Mbps,and ISD 104's incoming MCR is 96 kbps, then the buffers would be filledat a rate of 1.404 Mbps. It would take the buffers approximately 0.57seconds to become full at this rate. In this example, a measurement ofthe communication rate during the first 0.57 seconds would be 1.5 Mbps,and this would be an indication of the RD 108's incoming MCR, and ameasurement of the communication rate at any time after the first 0.57seconds would be 96 kbps, and this would be an indication of the ISD104's incoming MCR.

Therefore, in the case where PRD 150 is RD 108, the incoming MCR of PRD150 is indicated by PRD 150's incoming communication rate before thebuffer is full, and the incoming MCR of ISD 104 is indicated by PRD150's incoming communication rate after the buffer is full.

In the case where PRD 150 is ISD 104 this buffer does not exist and PRD150's incoming communication rate does not change, and remains equal toISD 104's incoming MCR.

Therefore, PRD 150's incoming MCR is equal to PRD 150's incomingcommunication rate until the time it would take RD 108's buffers to befilled, and ISD 104's incoming MCR is equal to PRD 150's incomingcommunication rate thereafter.

RDS 102 can thus determine whether PRD 150 is a Relay Device 108 bycomparing PRD 150's incoming communication rate at these two times.

In many cases, the communication rate from RD 108 to MH 110 does notexceed the ISD 104's outgoing MCR, because RD 108 would send to MH 110only the information it receives from ISD 104, and would not normallygenerate significant amounts of information by itself. However since, asdescribed above, RD 108 buffers communications between ISD 104 and MH110, it is possible to measure the outgoing MCR of RD 108 as follows.Some protocols contain a ‘flow control’ mechanism, which allows a devicereceiving information to signal to a device sending the information whento stop sending new information and when to resume sending. For example,in TCP if a receiving device sends an ACK segment with a ‘Window’ valueof zero, a sending device would normally stop sending new information,until it receives an ACK segment with a positive ‘Window’ value. A ‘flowcontrol’ mechanism may be used by MH 110 or RDS 102 to signal to RD 108to stop sending new information. This would cause RD 108's buffers to befilled by information, which RD 108 will continue to receive from ISD104, and would not send to MH 110. MH 110 or RDS 102 would then use the‘flow control’ mechanism to signal to RD 108 to resume sending newinformation. Since now RD 108 would send information from its localbuffers, until the buffers will be empty, a measurement of thecommunication rate would be an indication of the outgoing MCR of RD 108.

According to some embodiments of the present invention, checking whetherthe MCR of ISD 104 is different than the MCR of PRD 150 is done bydetecting an indication whether buffers in PRD 150 are being filled oremptied. For example, as described above, buffers in RD 108 would befilled if the incoming MCR of ISD 104 is smaller than the incoming MCRof PRD 150. In another example, as described above, buffers in RD 108would be emptied if the outgoing MCR of ISD 104 is smaller than theoutgoing MCR of PRD 150. Some protocols allow a device to advertise thecapacity of its buffers, or a derivative thereof, to other devices itcommunicates with, and this information may be used to estimate whethera device's buffers are filling or becoming empty. For example, in TCP adevice would advertise the amount of information it is willing toreceive in the ‘Window’ header of every ACK segment it sends. Changes inthe value of the ‘Window’ header normally reflect changes in thecapacity of the device's buffer. An increase in the ‘Window’ valueindicates the buffers are being emptied, while a decrease in the‘Window’ value indicates the buffers are being filled.

Therefore, a decreasing ‘Window’ value is a direct indication that PRD150's incoming MCR is larger than ISD 104's incoming MCR, meaning thatPRD 150 and ISD 104 are distinct devices (i.e. PRD 150 is a Relay Device108).

Another method of detecting an MCR is measuring the two latencies of twocommunications, which the only difference between them is the amount ofinformation contained in each, and then calculating the MCR from thedifference between the two latencies. As described above, the time iftakes for a communication to be transferred over a communication line isproportional to the amount of information contained in thecommunication. Therefore, the MCR is equal to the difference between theamounts of information in the two communications, divided by thedifference between the two latencies.

This method can also be used with RTT measurements, rather than latency.For example, the RTT of the ICMP echo mechanism, with a short Echomessage (e.g. 64 bytes), and the RTT with a long Echo message (e.g. 1500bytes), can be used to detect the device's MCR. It should be noted thatif the incoming and outgoing communications contain the same amount ofinformation, as in the ICMP echo example, the RTT method would provide acombined measurement of both the device's incoming and outgoing MCR. Onemethod to overcome this limitation is to make RTT measurements using aprotocol in which only one of the incoming and outgoing communicationscontain large amount of information. This would reduce the contributionof the other communication's latency to the RTT, and thus provide abetter approximation of the latency of the first communication. Forexample, a TCP SYN segment sent to a closed port would normally triggera segment containing the RST flag (RST segment). While the SYN segmentcan be of a size chosen by its sender, the RST segment would usually besmall (e.g. 40 bytes).

Another method of detecting an MCR is to estimate if from otherinformation known about the device. For example, finding the text ‘dsl’in the reverse DNS of the device's IP address indicates it is likely aDSL line, which usually has an incoming MCR of 500-2,500 kbps and anoutgoing MCR of 64-256 kbps. In another example, finding that the PRD150's administrator is AOL indicates it is likely connected through avoice-modem dial-up line (since this is the primary connectivity optionoffered by AOL), which usually has an incoming MCR of up to 56 kbps andan outgoing MCR of up to 33 kbps.

Two Devices Using the Same Relay Device

In another particular embodiment of the present invention, RDS 102detects that PRD 150 is a Relay Device 108 by determining that theoriginal sources of two information elements are two different devices,without requiring that one of the original sources be the PRD 150.

In this embodiment RDS 102 attempts to distinguish between the followingtwo cases:

FIG. 5A provides a diagram of the first case, in which ISD 104 sends twoinformation elements, PRIE1 and PRIE2, directly to MH 110, without usingRD 108. The two information elements are of a type that RD 108 mayrelay.

FIG. 5B provides a diagram of the second case, in which two differentdevices, ISD 104 and ISD2 106 each send an information element to MH110, wherein both information elements are relayed by RD 108.

RDS 102 distinguishes between the two cases as follows:

RDS 102 monitors communications of MHI 110 and therefore receives fromRD 108 two potentially relayed information elements (PRIE1 and PRIE2).RDS 102 then checks whether a feature (PRIE1-Feature) of an originalsource (PRIE2-Source) of PRIE1 and a feature (PRIE2-Feature) of anoriginal source (PRIE2-Source) of PRIE2 are Incompatible Features. Ifindeed PRIE1-Feature and PRIE2-Feature are Incompatible Features, thenit is more likely that the original source of PRIE1 and the source ofPRIE2 are different devices, which means the second case is more likely,which means that PRIE1 and PRIE2 have likely been relayed.

For simplicity reasons, the description of this embodiment contains onlythree devices, two of which use a relay device. In practice, there aremany devices connected to the Internet 100, and each of them may or maynot use one of several relay devices that are also connected to theInternet 100. More generally, this embodiment detects that a potentialrelay device is a relay device by determining that at least two originalsources of at least two potentially relayed information elements whichwere received from the potential relay device, have IncompatibleFeatures. Since by definition a single device is not likely to haveIncompatible Features, then it is likely that the two original sourcesare different devices, and therefore at least one of the sources is notthe potential relay device, which means the information element fromthis source has been relayed and the potential relay device is a relaydevice.

All methods described above for determining whether features areIncompatible Features are also applicable for this embodiment, mutatismutandis. For example, RDS 102 may compare the HTTP ‘User-Agent’ Headersprovided in PRIE1 and PRIE2, and if they are indicative of differentoperating systems determine that ISD 104 and ISD2 106 are distinctdevices and therefore PRD 150 is a Relay Device 108. In another example,RDS 102 may detect that the RTT of communications with PRIE1-Source andPRIE2-Source are significantly different. It should be noted, that inthis case each RTT is the sum of (a) the RTT between RD 108 and MH 110,and (b) the RTT between each original source and RD 108. Therefore, theRTT gap in this case is a result of differences between (c) the RTTbetween PRIE1-Source and RD 108, and (d) the RTT between PRIE2-Sourceand RD 108. The two RTTs are not necessarily significantly different,but in some cases they may be, allowing RDS 102 to detect an RTT gap.

Ensuring Communications with an Original Source

In some embodiments of the present invention, information relating tofeatures of devices is obtained from one or more new communications, andnot from the original communication or communications that containedNRIE and/or PRIE. For such new communications to be usable, it should beverified that these are communications with the original source of thePRIE and/or NRIE.

US Published Patent Application 20040243832 the entirety of which isherein incorporated by reference, discloses several methods fordetermining that two network messages originated from the same sender.While these methods refer to messages rather than information elementsor communications, and to senders rather than original sources, it willbe appreciated by someone skilled in the art that most of the methodsdescribed therein are applicable to detecting that two informationelements were sent by the same original source.

In one exemplary embodiment, ICMP packets and TCP/IP packets receivedwith the same source IP address or sent to the same destination IPaddress could be considered as communications with the same device.

In another exemplary embodiment, incoming TCP/IP packets belonging toone TCP connection could be considered to come from the same device.

In another exemplary embodiment, an HTTP response sent following an HTTPrequest, in accordance with the HTTP protocol could be considered as acommunication with the source of the HTTP request.

The System

FIG. 3 describes the components of the Relay Detection System 102 inaccordance with a particular embodiment of the present invention.

An Information Element Receiver 30 monitors communications that MH 110receives. It potentially also monitors communications that MH 110 sends.It potentially also monitors communications that Outgoing CommunicationSender 36 sends.

A Feature Incompatibility Analyzer 34 determines whether ISD-Feature andPRD-Feature are Incompatible Features.

An optional Feature Discovery Module 32 discovers the ISD-Feature and/orthe PRD-Feature.

An optional Outgoing Communication Sender 36 sends one or more OutgoingCommunications.

An optional Parameter Obtainer 38 obtains one or more parametersindicative of (a) the ISD-Feature, (b) the PRD-Feature and/or (c)whether ISD-Feature and PRD-Feature are Incompatible Features.

An optional Feature Database 40 contains a list of pairs of features andwhether they are Incompatible Features. For example, the FeatureDatabase 40 may contain a description of which HTML clients aresupported by each operating system.

Miscellaneous

It is to be understood that according to some embodiments, the presentinvention provides for using any combination of features or parametersdisclosed in the present document to be useful for determining if apotential relay device is a relay device and/or for determining ifreceived information elements were relayed by a relay device.

In some embodiments described above ISD-Feature and/or PRD-Feature wererelated to latency and/or to communication rate. It will be appreciatedby someone skilled in the art that these are specific cases of the moregeneral case in which ISD-Feature and/or PRD-Feature are related tocommunication performance. ‘Communication performance’ is a general termreferring to all the parameters describing the speed, rate, time,efficiency etc. of a communication.

In determining whether two features are Incompatible Features, RDS 102should consider the time at which each of the features was discovered.For example, if the two features are wall clock configurations equal to9:05 am and 10:05 am, and the second feature was discovered exactly onehour after the first, then the two features could not be consideredIncompatible Features, because the difference in time of discoverydirectly explains the difference in the features. However, if the sametwo features were discovered at approximately the same time, they couldbe considered Incompatible Features. In another example, if one featureis an RTT measurement of 900 milliseconds and the other feature is anRTT of 940 milliseconds, and the first feature was discovered 24 hoursafter the other, then the features are not necessarily IncompatibleFeatures, because network topology changes may account for thisdifference. However, if the same two features were discovered during thesame 100 millisecond period, the likelihood of topology changes issmaller, and thus the features are more likely to be IncompatibleFeatures.

If the features were discovered at nearly the same time, then RDS 102should consider whether these features are unlikely to concurrentlyrelate to the same device.

The numerous innovative teachings of the present application aredescribed with particular reference to a presently disclosed embodiment.However, it should be understood that this class of embodiments providesonly a few examples of the many advantageous uses of the innovativeteachings herein. In general, statements made in the specification ofthe present application do not necessarily delimit any of the variousclaimed inventions. Moreover, some statements may apply to someinventive features but not to others.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and therefore, the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

According to some embodiments, the term “unlikely” as used herein refersto a probability at most 40%.

In other embodiments, this probability is at most 30%.

In other embodiments, this probability is at most 20%.

In other embodiments, this probability is at most 10%.

In other embodiments, this probability is at most 5%.

In other embodiments, this probability is at most 1%.

In other embodiments, this probability is at most 1/2%.

Similarly, a “likely” event is an event that occurs with a probabilityof 100% minus the probability of the “unlikely” event.

According to some embodiments, a “single” device is physically onedevice. Nevertheless, it is recognized in the art that electronicdevices connected to data networks such as relay devices, monitoredhosts and information source devices are often a cluster of severalphysically different devices logically configured to present themselvesto a data network and/or devices on the data network as a “single”device. Thus, as used herein, a “single” device refers both to a singlephysical device as well as a plurality of physical devices logicallyconfigured to present themselves as a single device.

According to some embodiments, locations that are “different” as usedherein refers to places located in different countries.

According to some embodiments, locations that are “different” as usedherein refers to places located in different states.

According to some embodiments, locations that are “different” as usedherein refers to places located in different provinces.

According to some embodiments, locations that are “different” as usedherein refers to places located in different continents.

According to some embodiments, locations that are “different” as usedherein refers to places located in different time zones.

According to some embodiments, locations that are “different” as usedherein refers to location separated by a minimum of 100 kilometers, orby a minimum of 200 kilometers, or by a minimum of 1000 kilometers, orby a minimum of 2500 kilometers.

1. (canceled)
 2. A system, comprising: one or more processors, one ormore computer-readable memories, with program instructions stored on theone or more computer-readable memories, the one or more processorsconfigured to execute the program instructions to cause the system toperform the operations comprising: receiving a communication from adevice, the communication including a first device information and asecond device information; determining that the first device informationand the second device information are incompatible; and in response tothe determining that the first device information and the second deviceinformation are incompatible, determining that the device is a relaydevice.
 3. The system of claim 2, wherein the first device informationcorresponds to a first operating system and the second deviceinformation corresponds to a second operating system.
 4. The system ofclaim 2, wherein the first device information corresponds to a firstlocation and the second device information corresponds to a secondlocation.
 5. The system of claim 4, wherein the determining that thefirst device information corresponds to the first location includescross-referencing an internet protocol (IP) address informationassociated with the communication with an IP database, and wherein thedetermining that the second device information corresponds to the secondlocation includes analyzing location information in a header of thecommunication.
 6. The system of claim 2, wherein the first deviceinformation corresponds to a first sub-network and the second deviceinformation corresponds to a second sub-network.
 7. The system of claim2, wherein the first device information corresponds to a firstadministrator and the second device information corresponds to a secondadministrator.
 8. The system of claim 7, wherein the determining thatthe first device information corresponds to the first administratorincludes cross-referencing an internet protocol (IP) address informationassociated with the communication with an IP database, and wherein thedetermining that the second device information corresponds to the secondadministrator includes analyzing administrator information in a headerof the communication.
 9. A method comprising: receiving, by one or moreprocessors, a communication from a device, the communication including afirst device information and a second device information; determining,by one or more processors, that the first device information and thesecond device information are incompatible; and in response to thedetermining that the first device information and the second deviceinformation are incompatible, determining, by one or more processors,that the device is a relay device.
 10. The method of claim 9, whereinthe first device information corresponds to a first operating system andthe second device information corresponds to a second operating system.11. The method of claim 9, wherein the first device informationcorresponds to a first location and the second device informationcorresponds to a second location.
 12. The method of claim 11, whereinthe deteimining that the first device information corresponds to thefirst location includes cross-referencing an internet protocol (IP)address information associated with the communication with an IPdatabase, and wherein the determining that the second device informationcorresponds to the second location includes analyzing locationinformation in a header of the communication.
 13. The method of claim 9,wherein the first device information corresponds to a first sub-networkand the second device information corresponds to a second sub-network.14. The method of claim 9, wherein the first device informationcorresponds to a first administrator and the second device informationcorresponds to a second administrator.
 15. The method of claim 14,wherein the determining that the first device information corresponds tothe first administrator includes cross-referencing an internet protocol(IP) address information associated with the communication with an IPdatabase, and wherein the determining that the second device informationcorresponds to the second administrator includes analyzing administratorinformation in a header of the communication.
 16. A computer programproduct comprising: one or more computer-readable tangible storagedevices, and program instructions stored on at least one of the one ormore storage devices, the program instructions when executed cause amachine to perform operations comprising: receiving a communication froma device, the communication including a first device information and asecond device information; determining that the first device informationand the second device information are incompatible; and in response todetermining that the first device information and the second devicenation are incompatible, determining that the device is a relay device.17. The computer program product of claim 16, wherein the first deviceinformation corresponds to a first operating system and the seconddevice information corresponds to a second operating system.
 18. Thecomputer program product of claim 16, wherein the first deviceinformation corresponds to a first location and the second deviceinformation corresponds to a second location.
 19. The computer programproduct of claim 18, wherein the determining that the first deviceinformation corresponds to the first location includes cross-referencingan internet protocol (IP) address information associated with thecommunication with an IP database, and wherein the determining that thesecond device information corresponds to the second location includesanalyzing location information in a header of the communication.
 20. Thecomputer program product of claim 16, wherein the first deviceinformation corresponds to a first sub-network and the second deviceinformation corresponds to a second sub-network.
 21. The computerprogram product of claim 16, wherein the first device informationcorresponds to a first administrator and the second device informationcorresponds to a second administrator.